Energetics of magnetoelastic domains in ferromagnetic shape memory alloys

In recently developed ferromagnetic shape-memory alloys (e.g., NiMnGa or FePd compounds), martensitic transformations, hence large changes of shape, can be triggered by an applied magnetic field. The macroscopic deformations exhibited by such ferromagnetic martensites in response to applied magneto-mechanical loads correspond to easy deformation paths achieved through the cooperative evolution of microscopic magnetoelastic domains. We discuss a variational model for these materials which includes elastic, magnetocrystalline and magnetostatic energies. Macroscopic deformations are computed as averages on energy minimizing elastic domain structures. Magnetostriction curves are computed by solving parametrically a discrete, constrained optimization problem.